# std::to_string

From cppreference.com
< cpp‎ | string‎ | basic string

Defined in header `<string>` |  |
std::string to_string( int value ); | (1) | (since C++11)
std::string to_string( long value ); | (2) | (since C++11)
std::string to_string( long long value ); | (3) | (since C++11)
std::string to_string( unsigned value ); | (4) | (since C++11)
std::string to_string( unsigned long value ); | (5) | (since C++11)
std::string to_string( unsigned long long value ); | (6) | (since C++11)
std::string to_string( float value ); | (7) | (since C++11)
std::string to_string( double value ); | (8) | (since C++11)
std::string to_string( long double value ); | (9) | (since C++11)

Converts a numeric value to std::string.

Let `buf` be an internal to the conversion functions buffer, sufficiently large to contain the result of conversion. 1) Converts a signed integer to a string as if by std::sprintf(buf, "%d", value). 2) Converts a signed integer to a string as if by std::sprintf(buf, "%ld", value). 3) Converts a signed integer to a string as if by std::sprintf(buf, "%lld", value). 4) Converts an unsigned integer to a string as if by std::sprintf(buf, "%u", value). 5) Converts an unsigned integer to a string as if by std::sprintf(buf, "%lu", value). 6) Converts an unsigned integer to a string as if by std::sprintf(buf, "%llu", value). 7,8) Converts a floating point value to a string as if by std::sprintf(buf, "%f", value). 9) Converts a floating point value to a string as if by std::sprintf(buf, "%Lf", value). | (until C++26)
1-9) Converts a numeric value to a string as if by std::format("{}", value). | (since C++26)

### Parameters

value | - | a numeric value to convert

### Return value

A string holding the converted value.

### Exceptions

May throw std::bad_alloc from the std::string constructor.

### Notes

- With floating point types `std::to_string` may yield unexpected results as the number of significant digits in the returned string can be zero, see the example.
- The return value may differ significantly from what `std::cout` prints by default, see the example.

`std::to_string` relies on the current C locale for formatting purposes, and therefore concurrent calls to `std::to_string` from multiple threads may result in partial serialization of calls. The results of overloads for integer types do not rely on the current C locale, and thus implementations generally avoid access to the current C locale in these overloads for both correctness and performance. However, such avoidance is not guaranteed by the standard. | (until C++26)

C++17 provides `std::to_chars` as a higher-performance locale-independent alternative.

Feature-test macro | Value | Std | Feature
--- | --- | --- | ---
`__cpp_lib_to_string` | `202306L` | (C++26) | Redefining `std::to_string` in terms of std::format

### Example

Run this code

    #include <cstdio>
    #include <format>
    #include <initializer_list>
    #include <iostream>
    #include <string>

    #if __cpp_lib_to_string >= 202306L
    constexpr auto revision() { return " (post C++26)"; }
    #else
    constexpr auto revision() { return " (pre C++26)"; }
    #endif

    int main()
    {
        for (const double f : {1.23456789555555, 23.43, 1e-9, 1e40, 1e-40, 123456789.0})
        {
            std::cout << "to_string:\t" << std::to_string(f) << revision() << '\n';

            // Before C++26, the output of std::to_string matches std::printf.
            std::printf("printf:\t\t%f\n", f);

            // As of C++26, the output of std::to_string matches std::format.
            std::cout << std::format("format:\t\t{}\n", f);

            std::cout << "std::cout:\t" << f << "\n\n";
        }
    }

Possible output:

    to_string:      1.234568 (pre C++26)
    printf:         1.234568
    format:         1.23456789555555
    std::cout:      1.23457

    to_string:      23.430000 (pre C++26)
    printf:         23.430000
    format:         23.43
    std::cout:      23.43

    to_string:      0.000000 (pre C++26)
    printf:         0.000000
    format:         1e-09
    std::cout:      1e-09

    to_string:      10000000000000000303786028427003666890752.000000 (pre C++26)
    printf:         10000000000000000303786028427003666890752.000000
    format:         1e+40
    std::cout:      1e+40

    to_string:      0.000000 (pre C++26)
    printf:         0.000000
    format:         1e-40
    std::cout:      1e-40

    to_string:      123456789.000000 (pre C++26)
    printf:         123456789.000000
    format:         123456789
    std::cout:      1.23457e+08

### See also

to_wstring (C++11) | converts an integral or floating-point value to `wstring` (function)
stoulstoull (C++11)(C++11) | converts a string to an unsigned integer (function)
stoistolstoll (C++11)(C++11)(C++11) | converts a string to a signed integer (function)
stofstodstold (C++11)(C++11)(C++11) | converts a string to a floating point value (function)
to_chars (C++17) | converts an integer or floating-point value to a character sequence (function)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/string/basic_string/to_string&oldid=171806"